1. Field Of The Invention
This invention relates to apparatus and methods for injecting fluid into a well and flowing fluid back therefrom such as in microfrac tests (also called stress tests) and minifrac tests, and more particularly, to an injection manifold and method of use thereof which bypasses fluid from a supply pump back to a supply reservoir.
2. Description Of The Prior Art
In microfrac and minifrac tests, fluid is injected into the well at rates typically ranging from one to twenty gallons per minute to obtain certain reservoir characteristics. These flow rates are too low to be handled by standard multi-purpose pumps used at the well site.
One such pump typically used is the Halliburton HT-400 which is a positive displacement, high pressure, triplex plunger-type pump. In a prior method of injecting fluid in microfrac or minifrac tests, a small plunger kit is installed in the HT-400 pump fluid end to obtain the low flow rates desired for such tests. This small plunger kit, which effectively reduces the bore of the pump and thus the output capacity thereof, is relatively expensive. Further, such kits typically require two to three hours for installation and one to two hours for removal so that the pump can again be used for its normal purposes. This is a disadvantage because the pump is tied up and cannot be used on other cementing or fracturing jobs until the small plunger kit is removed. Further, accurate and quick changes in the flow rate are still difficult to make. An additional disadvantage is that the rangeability of the small plunger kit is limited. This rangeability limitation requires different sizes of plungers for different flow rate ranges, which, of course, results in the cost and time disadvantages already mentioned.
Accordingly, there is a need for an apparatus and method of injecting low flow rates of fluid into wells during microfrac and minifrac tests which do not involve the time and cost burden of refitting a pump with a small plunger kit. The injection manifold of the present invention includes a bypass valve which adjusts the discharge pressure of the pump and allows the relatively low one to twenty gallon per minute flow rates to be injected into the pump without the necessity of installing a small plunger kit on the pump.